The conventional telephone answering machine has a "stop" or "off" mode in which the automatic answering function is disabled (as for example when the user is present and desires to answer phone calls himself) and has provisions enabling the machine to be manually placed in the answer mode when it is desired to have the machine automatically answer telephone calls. For those instances where the user leaves his home or office and forgets to switch the machine to the automatic answer mode, some conventional machines have provisions which enable the machine to be placed in the automatic answer mode by calling from a remote telephone. For that purpose, such conventional machines are constructed to detect ringing signals that recur for a longer period than is normal for the usual telephone call where the calling party most often hangs up the phone after four or five rings. Where the ring signals are permitted to recur over a period of about one minute, the conventional machine is constructed to switch to the automatic answer mode a given period after the recurrence of the ring signals has stopped. To ensure that the conventional machine has switched to the automatic answer mode, another call must be made and the caller must then wait for the outgoing announcement to begin.
The essential conditions for the conventional machine to switch to the automatic answer mode are (1) that the ring signals recur over at least a specified minimum period of time (2) that the phone call be terminated, and (3) that a specified time elapse from the cessation of the ring signals before the machine switches to the automatic answer mode. The conventional arrangement necessitates a second phone call to ensure that the change to the automatic answer mode has occurred because the phone will continue to ring so long as the first phone call is in progress--that is, in the conventional arrangement, the switch to the automatic answer mode cannot occur during the first phone call because the calling phone must be hung up to stop the phone from ringing. If the caller does not make the second phone call, then the caller must make certain that the ring signals recur during the first phone call for at least the minimum required time period to insure the subsequent switch to the automatic answer mode.